Hi Folks,

Have a bit of curly question with regards to the best glide speed and flying with a tailwind.

Firstly, does flying at the best glide speed/lift-drag ratio give you the best air time?

My thought is that it would, based on the fact that any deviation from the best glide speed results in a higher angle of descent and hence a greater ROD.

If, I haven't got the above wrong, then how does flying at a speed slower than the best glide in a tailwind increase your range? Which would imply that flying at a speed slower than the best l/d ratio would give you the best air time.

I understand how the concept works when you have power, but not for glide.

Thanks!

Gidday Basketball,

In no wind, if you glide at the best lift-drag ratio speed you will certainly cover the greatest distance in the glide from any given height. However that is not necessarily the longest time in the air. By gliding a little slower than the best lift-drag ratio speed you will cover less distance because your gliding angle will be steeper. However, even though you are gliding down a steeper path, the lower speed will result in a longer time to hit the ground. In a tail wind, that extra time in the air will allow the wind to carry you further forward. There will always be a particular slower speed where the extra time in the air will result in the wind actually carrying you further than the nil-wind distance.

In practice, of course, it would be quite difficult to judge how much slower you would need to fly in a tailwind. That is really a function of both your gliding speed and the strength of the tail-wind component.

Thanks for the explanation Bob!

Me and a few blokes at the school were busting our heads over this one.